Trump Accuses Cruz of Stealing Iowa Caucus Victory

"There is no such thing as an election violation related to frequency of voting," Pate writes. "Any insinuation or statement to the contrary is wrong and I believe it is not in keeping in the spirit of the Iowa Caucuses."

Matt Schultz, the Cruz campaign’s Iowa state chairman and a former Iowa secretary of state, told the New York Times that mailers such as those Trump is lambasting "are a common practice to increase voter turnout".

"Our mailer was modeled after the very successful 2014 mailers that the Republican Party of Iowa distributed to motivate Republican voters to vote, and which helped elect numerous Republican candidates during that cycle," Schultz said.

Ted Cruz won in Iowa with 27.6% of the vote, followed by Donald Trump with 24.3%, Marco Rubio with 23.1%, and Ben Carson with 9.3%.